Compound Interest Calculator
See how a lump sum and regular deposits grow with compound interest at any frequency, with a full yearly breakdown.
About this calculator
Compound interest is interest earned on both your original principal and the interest that has already accumulated — the reason long-term investing is so powerful. This free compound interest calculator shows the final value of a lump sum (and optional monthly deposits) using the formula A = P(1 + r/n)^(nt), across daily, monthly, quarterly, semi-annual, or annual compounding.
Enter your principal, annual interest rate, time period, and compounding frequency to see the maturity amount, total interest earned, and the Effective Annual Rate. A year-by-year breakdown reveals how growth accelerates over time. It is ideal for planning savings, fixed deposits, or any investment that compounds. All maths runs locally in your browser; results are estimates, so confirm actual returns and tax treatment with your bank or financial advisor.
Why use this tool
See compounding work
Watch how interest on interest grows a principal over time.
Flexible frequency
Model yearly, half-yearly, quarterly or monthly compounding.
Clear breakdown
Separate your principal from the interest earned.
Common use cases
- Project growth of a fixed deposit or savings
- Compare compounding frequencies
- Plan a lump-sum investment
- Understand long-term wealth growth
Frequently asked questions
A = P(1 + r/n)^(nt), where A is the final amount, P is the principal, r is the annual rate as a decimal, n is the number of times interest compounds per year, and t is the number of years.
Simple interest is calculated only on the original principal, while compound interest is calculated on the principal plus all previously earned interest — so it grows faster, especially over long periods.
The more often interest compounds (daily vs annually), the more you earn, because interest starts earning interest sooner. The effect is shown by the Effective Annual Rate (EAR).
EAR is the actual yearly rate once compounding is included: EAR = (1 + r/n)^n − 1. A 12% nominal rate compounded monthly has an EAR of about 12.68%.
Yes. Add an optional monthly deposit and the calculator includes those recurring contributions in the growth, showing how regular investing accelerates your balance.